buckingham



Jan. 24, 1956 w. D. BUCKINGHAM POLAR RELAY Filed May 1, 1953 FIG.4

INVENTOR.

W. D. BUCKINGHAM ATTORNEY United States Patent POLAR RELAY William D.Buckingham, Southampton, N. Y., assignor to The Western Union TelegraphCompany, New York, N. Y., a corporation of New York Application May 1,1953, Serial No. 352,355

12 Claims. (Cl. 200-87) My invention relates to a high-speed vacuumrelay in which the armature is a ball or equivalent member composed ofmagnetizable material disposed in an electromagnetic field and movablerelative to fixed contact elements by the ma'gnetomotive force of thefield to open and close circuits controlled by the relay, and moreparticularly to an improved form of polar relay of the characterdisclosed in my copending application Serial No. 306,690, filed August27, 1952, the disclosure of which is incorporated herein by reference.

Among the objects of the present invention are to provide an improvedrelay unit of the character described, in which a more eflicientmagnetic circuit is provided and considerably more space for the relaycoils is obtained without enlargement of the overall dimensions of therelay unit; in which a substantial increase in the stabilityandsensitivlty of the relay is achieved and sticking of the contacts isprevented; to provide means for preventing contact bounce; and theprovision of improved means operativeto prevent any undesired signalbias in the operation ofthe relay.

These and other objects and advantages of the invention will be apparentfrom the following detailed description of an illustrative embodimentthereof, taken in connection with'the accompanying drawings in which:

Fig. l is'a perspective view of a complete relay unit "embodying thefeatures of the instant invention;

Fig. 2 is a cross-sectional view taken along the line '22 of 'Fig. 1;

Fig. 3'is a'sectional view taken along the line 3-3 of Fig. 2;

Fig. 4 is an enlarged view of the permanent magnet 'struc'tur'e'andrelay contact assembly within an evacuated tube, removed from the unit;and

v Fig. 5 is a view'taken along the line 5 5 of Fig. 4, "showing certaindetails of the relay contact structure.

Referring particularly to Figs. 1 to 3, the casing of the relay unitcomprises a rectangular wall, portion composed of a magnetizablematerial oflowreluctance, such as-iron, having a cover 11 and a bottomplate member 12. The members 11 and 12-pre ferably are of metal. The.cover has a circular opening 11a therein for a purpose hereinafterexplained. As seen in'Fig. 3, the bottom plate member 12 receives aduodecal plug 15 of Bakelite or other suitable insulating material,which c-arries-anumber of electrical contactprongs 16 adapted tobeplugged into a conventional socket. -A lower tubular portion 15aof'the-plug body has formed thereon a key or spline (not shown) which isreceived within a keyway in the socket thereby to insure that theprongs16 will enter theproper contact sleeves inthe socket when the plug isinserted. As seen inFig.-2, two arcuate strips 15 of Bakelite or othersuitable insulatingmaterial, andwhich havetapered edge portions, areinterposed between the inner ends oripole .pieces of twolaminatedmagnetic cores 18 to position-the cores and also the two bobbins 23thatcarry-the relay windings. A central opening through the unitreceives the removable tube 25 that encloses the armature and contactassembly of the relay. The tube envelope necessarily is composed of anon-magnetic material, and usually is of glass.

Figs. 2 and 3 show a magnetic circuit having a greatly increasedefficiency. The laminated cores 18 each is in contact at its outer endwith the comparatively thin laminated wall 10 of the casing, so that therelay case provides a return path of low reluctance for the magneticflux. The inner ends or poles of the cores 18 are tapered and arearcuate, as seen in Fig. 2, thereby to concentrate the flux field in anoperating gap immediately adjacent to the wall of the glass tube 25 andthe pole pieces 29 (Fig. 4) of the permanent magnet structure within thetube. Referring to Fig. 2, the two opposite laminated wall portions ofthe casing 12 which are parallel to the longitudinal axis of the cores18 each extends in a vertical plane as viewed when looking down on thefigure, and does not extend appreciably in a horizontal plane. That isto say, the individual laminations or layers of these portions aredisposed edgewise instead of flat with respect to the cores and hence donot extend in a horizontal plane towards the cores as in the usualarrangement of magnetic core structures. Therefore the distance, andhence the magnetic leakage path, between the inner ends or poles of eachof the cores and the wall portions which comprise the return circuit isgreatly increased and is more than one and one-half times, and nearlytwice, the distance across the operating gap between the poles, withconsequent reduction in magnetic leakage and increase in the amount offlux in the operating gap. With a given number of magnetizing ampereturns applied, this magnetic circuit will, on the average, produce a 40%stronger magnetic field to move the ball armature 35 of the relay thanwould be produced by a conventional laminated core, for example, asshown in Fig. 23 of my aforesaid application, in which the leakage pathfrom the operating gap 'at'the poles to the adjacent legs of the core ismuch shorter than that present in the structure of the instant case.

The improved magnetic structure, moreover, provides almost three timesas much coil winding space without substantially increasing the overalloutside dimensions of the unit. It will be seen from Figs. 2 and 3 thatfour different relay windings 19 to 22, such as are commonly employed intelegraph relays, readily are accommodated by the space availablebetween the core structure 18 and the casing 10. Each relay windingcomprises two seriesconnected coils respectively positioned in oppositehalves of the casing'as seen in the figures. The coils are wound on twoBakelite bobbins, indicated at 23, and preferably are separated from theBakelite bobbins by cellulose acetate sheets; sheets .23 Of'thismaterial also are used to separate the various layers of the coilwindings. The pieces 14 of Bakelite or other suitable material, shown inFig. 2, orient the bobbins and their coils properly for the pouring of athermosettingplastic filler 24. The Bakelite structure comprising theinner end wallportions of the bobbins 23 may carry eyelets of nickel orthe like to pro videterminal pointsboth for interconnections of thecoils and'to facilitate connections to the prongs 16 of the relay base.

The laminated wall portion 10 of the casing may be fabricated from alength of sheet iron of proper width which'is wrapped around a form andspot welded or otherwise fastened'to form'the four sides of a box. The

bottom plate 12 which is preferably, although not necessarily, ofsimilar material is drawn in a hydraulic press andpierced to form theopening for the duodecal plug 15. The bottom plate is spot welded orotherwise secured to the side wall before assembly of the coils in thecasing, and this'casingassembly preferably is nickel plated nated cores18 and spacer elements 14, then are assembled in the casing, and allconnections between coils and between the windings and the prongs 16 ofthe plug 15 are made, including a ground lead between the casing and oneprong of the plug.

Prior to pouring the plastic filler 24, a cylindrical rod or core plug(not shown) is inserted so that it extends vertically through the casingand is positioned centrally within the opening in the tubular portion aof the base 15, passing between the inner curved ends of the pole pieces18 and the arcuate spacers 14, thereby to provide a through apertureslightly larger in diameter than the outer diameter of the tube orcapsule subsequently to be inserted. Stearic acid, glyceryl stearate,silicone greases or other known mold-release agents are applied to thecore plug to enable ready withdrawal thereof after the molding orfilling operation, or a core plug composed of a material which requiresno mold-release agent, such as fiuoroethylene or Teflon, may be used.

With the core plug inserted and the outside of the casing 10 greasedwith a substance such as a silicone grease to prevent any excess fillermaterial from sticking to the outside of the casing, the unit is readyfor pouring. The electromagnetic structure is thus embedded in a moldedbody of a suitable thermosetting insulating material which has highdielectric strength, low power factor, high heat resistance and high areresistance, and which may be poured as a liquid (preferably heated) andwhich thereafter hardens. Such a material may comprise celluloseacetate, neoprene or synthetic rubber, or other non-aging plasticinsulating compound. Preferably, styrene plastic such as Melpak IV or anethoxyline resin such as Araldite E1l0 is employed, with an associatedhardener such as Araldite HN-90l. The E-llO is a hard substance whichmelts at around 100 C. The proper amount of HN-901, a white powderysubstance, is added at between 100 and 120 C. and allowed to dissolve inthe molten plastic. While this is taking place, the relay to be pouredis placed in an oven and allowed to heat up to nearly the sametemperature. When the hardener has completely dissolved, the solution isallowed to rise in temperature to not more than 130 C. and then ispoured into the relay case. Care must be taken to pour slowly so thatall air is forced out of the case to prevent voids. When pouring iscompleted, the unit is placed in the oven and cured for about 16 hoursat -1l0 to 120 C. After curing, the plastic is slightly rubbery untilcool, when it becomes very hard, after which the top surface is smoothedoff and the top cover 11 is put on. The cover may be held in place inany suitable manner, for example, by escutcheon pins. The relay is nowready for the insertion of the tube 25 and its associated elements.

Fig. 4 is a greatly enlarged view of the tube 25 and its enclosedelements. Two pole pieces 29 initially are formed from a small round rodof magnetic material such as soft iron which has the lower end thereofwelded to the end of a slightly smaller round rod of stainless steel orother non-magnetic metal or alloy. A hole at 37 and two smaller holesbelow the first hole are drilled transversely through the rod from whichthe pole pieces 29 are formed, and this rod and the attached stainlesssteel rod are sawed in half throughout their combined length to providethe pole pieces 29 and two stainless steel strips 30. Within the smallholes in the pole pieces 29 are inserted short rods 39 which preferablyare composed of tungsten carbide. These rods or inserts are welded tothe pole pieces, and their inner faces are ground to form flat contactsurfaces, flush with the inner walls of the pole pieces, which fiatsurfaces are alternately contacted by the ball armature 35 as signals ofopposite polarity are received by the operate windings of the relay.

Between the stainless steel strips is inserted a flat strip 31 ofpermanent magnet material, for example, a

copper-nickel-iron alloy such as Cunife or an aluminum-nickel-cobaltalloy such as Alnico, on the end of which has been welded a thin piece32 of tungsten carbide or other suitable contact material on which theball 35 rests. The strip 31 comprises the permanent magnet of themagnetic circuit within the tube, and also connects the contact material32 to one of the terminals 28 of the tube. Flat strips 33 of mica orother suitable dielectric material insulate the magnet 31 and contactmaterial 32 from the stainless steel strips 30, which steel stripsrespectively connect the contact members 39 to two other terminals 28 ofthe tube.

The assembly of elements 30 to 33 is enclosed within an outercylindrical shell 34 which is spaced therefrom, and in this space iscast glass or Mycalex or other plastic molding compound which insulatesthe enclosed elements from the shell 34 and also locks them in positionrelative to each other. The strip 31 usually is magnetized after theassembly is completed and sealed in the glass tube. The shell 34preferably is iron although it may be of any other metal or material,not necessarily magnetic, although it is advantageous to employ amagnetic material since it provides a return path for the flux of thepermanent magnet 31. The lead-in wires which pass through the tube mayreadily be spot welded to the strip 31 and the legs 30 of stainlesssteel prior to insertion of the assembly within the tube. The .largehole which was drilled at 37 causes the pole pieces 29 to be cut awaysomewhat and this produces a desired concentration of flux around theball 35. A short cylindrical rod 40 of insulating material is wedgedbetween the arcuate surfaces at 37 to maintain uniform spacing of thepole pieces and also the contact elements 39.

The ball 35 is held in position on the member 32 by the magneticattraction of the small permanent magnet 31, the ball having an inducedvertical magnetic polarization. When the contact assembly is traversedby the horizontal magnetic fiux in the operating gap of the relay unit,the ball serves the dual function of armature and moving contact, androlls to one side contact 39 or the other, depending upon the directionof current flow through the relay coils, and switches the connectionfrom the magnet 31, through the ball, to the proper side contact. Thebase 27 of the glass tube carries three small machine screws 28, withthe lead-in wires of the tube connected under the heads of the screws.The threadedends of the screws screw into inserts within the molded body24, one of which inserts is seen in Fig. 3, thereby to secure the tubein proper position Within the central aperture in the relay unit, theinserts also serving to electrically connect the terminals of the tubeto the prongs 16 of the plug 15. During operation of the ball armature35 at high speeds, there is a tendency for the pole pieces 29 to bedeflected slightly by the force of impact and cause contact bouncebetween the ball 35 and its contact elements 39. To obviate this, apiece of energy-absorbent material 41 is wedged between the pole pieces29 and the tube 35. This material is characterized in that itsubstantially absorbs the shock applied to the pole pieces duringoperation of the relay and reduces rebound against the ball armature, sothat contact bounce is substantially reduced. Preferably, this materialis composed of fluorethylene or Teflon.

After the contact assembly above described is inserted within the tube25, the latter is exhausted to a high degree of vacuum, less than onemicron of mercury pressure, and a getter pill within the tube is firedto give a higher degree of vacuum and to act as a clean-up agent. Thetube is then sealed off in known manner, thereby to insure that noarcing will occur between the contact elements within the tube, afterwhich the press of the tube is cemented or otherwise mounted within thebase 26. The degree of vacuum should, of course, be sufliciently high toinsure that no arcing will occur at the potential of the currentcontrolled by the contact assembly; potentials in excess of 1000 voltsmay be used with the contact assembly when the tube is exhausted to thedegree above mentioned.

In order to magnetically center the relay so that it will operatewithout bias, an external bias-adjusting magnet 45 disposed within theaperture in the relay unit, Fig. 3, is provided. The magnet preferablyis a. permanent magnet and is a U type in polarization, and fits overthe end of the relay capsule 25 on its longitudinal axis. Thisbias-adjusing magnet preferably, although not necessarily, is composedof Alnico V. In contact with and bearing on the upper end of the magnetis a short length of tubing 47 composed of natural or artificial rubberor other suitable resilient material. For clarity the member 47 is shownslightly spaced from the wall of the aperture, but in practice it isslightly wedged within the aperture and is somewhat compressed by meansof a brass washer 46 and a coil spring 48, the lower end of which bearsagainst the washer 46 and the upper end of which is held against the topof the casing. The members 47 and 48 resiliently retain thebias-adjusting magnet 45 in any of its adjusted positions. This magnethas means for enabling it to be oriented through the aperture in therelay unit, such as a slot 49 in the upper surface thereof, and biasadjustment can be made with a small screw driver which is passed throughthe access hole 11a in the top of the case and through the spring 48 andthe openings in the members 46 and 47. Rotation of the magnet 45 to theproper oriented position causes .the ball armature 24 to be magneticallycentered so that the relay will operate without bias.

A substantial increase in the stability and sensitivity of the vacuumrelay has been achieved by processing the steel ball 24 so that itsmagnetic characteristics are uniform and to cause it to possess only therequired degree of magnetic retentivity or hardness. Prior to this itwas found that some of the relays were variable in theircharacteristics, for example, a relay which at one time could beoperated by a Z-milliampere current through its coils might on anotheroccasion require several times this current. By measuring the magneticcharacteristics of its steel ball armature, this difiiculty was found tobe due to an excessive permanent magnetism which built up in the ball.As the ball normally revolves during operation, the strongly magnetizedball would occasionally orient itself so that its magnetism would opposethat of the applied field and produce an apparent sticking of the relaycontacts. It was attempted to solve this difficulty by magneticallysoftening the balls so that they would not retain magnetism. These ballswere unsatisfactory, however, for they would not revolve duringoperation and pounded hats at the contact points. The slight turning ofthe ball at each operation is apparently caused by interaction betweenthe alternating and polarizing magnetic fields applied to the ball andthe magnetism remaining in the ball from the preceding operation. Thesedifficulties were solvedby controlling the magnetic hardness of theballs to a point where they retain s'ufiicient magnetism to causerotation but not sticking. Fortunately, the required degree of hardnessdoes not seem to be critical and can be secured by a simple annealingprocess.

The process of annealing to secure magnetic softness also makes theballs mechanically soft, and after a long period of use such balls mayshow a slight pattern on their surface which appears to be made up ofinnumerable very small flat areas. To avoid this effect, the balls maybe plated with a hard coating such as chromium, molybdenum, rhodium,tungsten carbide or the like. Instead of a-coating the balls may becase-hardened after annealing, by a nitriding process. This consists inheating them for several hours in an atmosphere of ammonia gas. Thenitrogen of the gas combines with the surface layer of the steel ball toproduce an exceedingly hard nitride coating. Tests on balls thus treatedhave shown that hundreds of millions of relay operations have failed toproduce measurable wear, and results from the tests indicate thatbillions of operating cycles will be obtained from the relays.

There is no maintenance required during the life of these relays. Sincethe relays are protected from outside influence such as dust, dirt,moisture, corrosive gases which might cause early and unpredictablefailures of contacts, bearings or windings, and since the contacts arethe only wearing parts, the relays have very uniform lifecharacteristics. It is expected that the life of the relay contactsunder specific operating conditions can be predicted so that the tube 25can be replaced on a schedule in advance of any failure.

Preferably, as hereinbefore set forth, the tube or envelope whichcontains the contact assembly is exhausted to a. high degree of vacuumso that the gas pressure is so low as to insure that no ionization andarcing will occur. However, it is known in the art that if gases inwhich the atoms have few electrons, such as hydrogen and helium, areunder high pressure, for example, of the order of 15 atmospheres, themean free path of the electrons is decreased to a value such that thereis little or no likelihood that ionization and arcing will occur at theoperating potentials employed, and therefore there will be no arcingbetween the elements of the contact assembly. it will be understood thatthe tube necessarily would be composed of a heavier glass and thatspecial precautions would be taken for sealing the tube when such highpressures are employed. For brevity in certain of the claims, theexpression non-ionizable medium is used to define the condition in whichthe gas pressure is either below or above the range of pressures whichwould enable ionization and arcing to occur at the potentials with whichthe tube and its contact assembly are adapted to be used. Variousmodifications of the relay and contact assernbly of the embodiment shownin the drawings, and various equivalents or substitutes for the elementsthereof, readily will occur to those versed in the art without departingfrom the spirit or scope of the instant invention. The disclosure,therefore, is for the purpose of illustrating the principles of theinvention which is not to be regarded as limited except as indicated bythe scope of the appended claims.

What is claimed is:

l. A polar relay unit comprising a casing in which the side wall thereofis substantially composed of a laminated magnetic material of lowreluctance, magnetic core structure within said casing comprising twolaminated legs respectively having two ends thereof positioned adjacentto'each other in spaced relation to provide poles with an operating gapbetween them, the otherends of said legs respectively adjoining two sideportions of the laminated wall structure to provide a magnetic fluxreturn path of low reluctance in series with said legs, operate windingspositioned around said legs and responsive to received signals forinducing opposite magnetic poles respectively therein, said poles beingspaced from said wall structure a distance which is substantiallygreater than that across said operating gap to minimize magnetic leakageto the return path, said unit having an aperture extending therein andtransversely intersecting said operating gap, a sealed tube composed ofnon-magnetic material and a permanent magnet and an associated armatureand contact assembly in a non-ionizable medium enclosed within the tube,the tube being removably positioned in said aperture in the unit withone pole of said permanent magnet adjacent to said opposite magneticpoles and the armature subject to the resultant flux field establishedin the operating gap.

2. A relay unit according to claim 1, in which said poles of themagnetic core structure are substantially equidistant from the nearestportions of the laminated wall structure and are spaced therefrom adistance greater than one and one-half times the distance across theoperating gap between the poles.

3. A relay unit according to claim 1, in which said legs are in axialalignment with each other and the periphery of the laminated side wallof the casing is substantially rectangular in outline, said casinghaving two opposite side wall portions each having the laminationsthereof extending in a plane substantially parallel to the axis of saidlegs and spaced from the legs a distance which is substantially greaterthan the distance across said operating flux gap to minimize magneticleakage to the return path provided by the casing.

4. A polar relay unit comprising a molded body of insulating material,magnetic core structure within said body comprising two legsrespectively having two ends thereof positioned adjacent to each otherin spaced relation to provide poles with an operating gap between them,operate windings positioned around said legs and responsive to receivedsignals for inducing opposite magnetic poles respectively therein, saidbody having an aperture extending therethrough and intersecting saidoperating gap, a sealed tube composed of non-magnetic material and apermanent magnet and an associated armature and contact assembly in anon-ionizable medium enclosed within the tube, the tube being removablypositioned in said aperture in the body with one pole of said permanentmagnet adjacent to said opposite magnetic poles and the armature subjectto the resultant flux field established in the operating gap, a biasingmagnet positioned in said aperture of the body with the external fieldof the magnet adjacent to said operating gap, said last named magnethaving means for enabling it to be oriented, through said aperture, topre- Vent undesired signal bias during operation of said armature.

5. A relay unit according to claim 4, in which said biasing magnet is apermanent magnet with the opposite poles thereof positioned adjacent tosaid operating gap, said magnet havingmeans for enabling its poles to berotated, through said aperture, to orient the external field of themagnet.

6. A relay unit according to claim 4, including resilient means withinsaid aperture for maintaining the biasing magnet in any position towhich it is oriented.

7. A relay unit according to claim 4, in which said armature comprises aball of magnetic material attracted by said permanent magnet androtatable to selectively engage opposed contacts during operation of therelay, said ball having magnetic retentivity to cause the ball torevolve during successive operations of the relay by the interactionbetween the magnetic field applied to the ball and the magnetismremaining in the ball.

8. A relay unit according to claim 5, in which the biasing magnet hastwo legs positioned over an adjacent end of the sealed tube ofnon-magnetic material.

9. A polar relay unit comprising a casing, magnetic core structurewithin said casing comprising two laminated legs respectively having twoends thereof positioned adjacent to each other in spaced relation toprovide poles with an operating gap between them, operate windingspositioned around said legs and responsive to received signals forinducing opposite magnetic poles respectively therein, said casing beingfilled with a solid insulating compound in which said core structure andrelay windings are embedded, said unit including its casing having anaperture extending therethrough and intersecting said operating gap, asealed tube composed of non-magnetic material and a permanent magnet andan associated armature and contact assembly in a non-ionizable mediumenclosed within the tube, the tube being removably positioned in saidaperture in the unit with one pole of said permanent magnet adjacent tosaid opposite magnetic poles and the armature subject to the resultantfiux field established in the operating gap, a biasing magnet positionedin said aperture of the unit with the external field of the magnetadjacent to said operating gap, said last named magnet having means forenabling it to be oriented, through said aperture, to prevent undesiredsignal bias during operation of said armature.

10. A polar relay contact unit comprising a sealed tube composed ofnon-magnetic material, a permanent magnet and an associated armature andcontact assembly in a non-ionizable medium enclosed within the tube,said contact assembly including an element having a contact surfaceadjacent to one pole of said magnet and two other conducting members'ofmagnetizable material respectively having oppositely disposed contactsurfaces, said armature comprising a conductive ball of magneticmaterial attracted by said permanent magnet and rotatable on said firstnamed contact surface to selectively contact said oppositely disposedcontact surfaces in response to changes in polarity in the magnetic fluxfield of a polar relay for closing a circuit between either of thesesurfaces and said first named contact surface, said ball having magneticretentivity to cause the ball to revolve during successive operations ofthe relay by the interaction between the magnetic field applied to theball and the magnetism remaining in the ball, said ball being annealedto limit its retentivity to a predetermined value to prevent stickingbetween the ball and either of said oppositely disposed contactsurfaces.

11. A polar relay contact unit according to claim 10, in which saidarmature is an annealed steel ball having a hard outer surface tominimize wear.

12. A polar relay contact unit according to claim 11, in which saidannealed ball is case hardened to provide a hard outer surface tominimize wear.

References Cited in the file of this patent UNITED STATES PATENTS547,537 Biddle et a1. Oct. 8, 1895 684,378 Potter Oct. 8, 1901 2,167,588Rozumek July 25, 1939 2,245,391 Dickten, Jr. -June 10, 1941 FOREIGNPATENTS 428,146 France -June 14, 1911 577,924 Germany "June 7, 1933

